1. Field of the Invention
The invention relates to a differential signal transmission cable and a method of making the differential signal transmission cable.
2. Description of the Related Art
A method of making parallel-type coaxial cable with a low skew is known that a foamed insulating material is collectively extrusion-molded on a pair of inner conductors extending in parallel to have a circular or elliptical shape in sectional view, an outer conductor is then formed on the periphery of the foamed insulating material, and the outer conductor and the foamed insulating material are tightly covered with an insulating jacket (see JP-A-2001-035270).
By means of the method disclosed in JP-A-2001-035270, it is possible to provide a cable with a reduced dispersion of foaming degree in the longitudinal direction of the cable. Thus, such a low skew can be obtained that cannot be reached by a conventional cable (or a twinax cable) that two foamed insulated wires with single cores are arranged in parallel so as to be a pair.